A chemical smell in the swamp and suspicious behavior on their neighbors' property alert twelve-year-old sibling investigators Peter, Jason, and Kim to the possibility of a threat to the environment.
While learning the rugged sport of spelunking on a visit to King Cave, Peter, Kim, and Jason face an even bigger challenge when they find a mysterious trail of cartridges in a deep underground tunnel.
Accompanying their parents on an archeological dig at the site of an ancient Hopewell Indian burial ground, sibling investigators Jason, Peter, and Kim discover that someone does not want the area disturbed.
When twelve-year-old twins Peter and Jason and their stepsister Kim visit Canada's North Woods in the middle of winter, they investigate the disappearance of an elderly woman hermit.
Twelve-year-old siblings Jason, Peter, and Kim help their parents investigate the water shortage in a desert town in California, where an important stream has mysteriously disappeared.
Peter, Kim, and Jason become involved in a dangerous adventure when they accompany their parents on a research assignment about whales and the laws that protect them.